Oven dishes are made of clay that is very resilient. They are sturdy and beautifully decorated, and the glaze on them has a lovely crackle effect.
Like any ceramic dish, they don't like sudden temperature changes- thermal shock may break them so never pour cold water over a hot dish or put it into the fridge before it cools down.
Because the glaze is crackled, food cooked in them may stain the crackle lines with time. It is advised to line the dishes with baking paper of foil, especially if you're cooking dark coloured foods like beetroot, aubergines etc, using spices that stain, or roast meat or fish that produces lots of juices.